Wrong Speed Conversion?

[Winged Wolf]

So I was doing a little over-the-pacific flight in the A320, learning to use the autopilot and noticed something interesting.

The internet says that the most efficient flight for this plane is at a speed of 450kts at an altitude of 37000ft. A quick Google search reveals that 350kts is equal to 230m/s (for reference, speed of sound is 340m/s).

The thing is, when I input 450kts in the autopilot and convert that number to mach, it converts it as 1.32 Ma, over the speed of sound. This is not just an error converting to mach as when I approach 300kts I won't stop getting "overspeed" warnings.

I am pretty new to the flight simulation genre (it is kind of a genre by itself) and I realize this is probably an error in my part, if anyone can explain this behavior to me I'd really appreciate it!

Here there's a little image, with some data explained for reference.

[Maki Nishikino]

Because what you're seeing on the airspeed indicator is indicated airspeed, this will be lower as you climb. You swap over to true airspeed / mach number. 1.32 mach is way too fast. I don't know the exact numbers but it should be in the .80 range.

[Kosmozuikis]

Cruise speed should be something like 320 knots. 250 knots bellow 10k feet i think.
And there's ground speed and true speed. 1,32 mach is way too much that plane can't go nowhere near that fast.
1 mach is ~650 knots, can't recall the exact number. 1,32 mach is insane, even not every fighter jet can go that fast.
I guess in the game it's a bug and it shows you ground speed which in this case should be something around 450 knots.

[Winged Wolf]

Originally posted by Maki Nishikino:

Because what you're seeing on the airspeed indicator is indicated airspeed, this will be lower as you climb. You swap over to true airspeed / mach number. 1.32 mach is way too fast. I don't know the exact numbers but it should be in the .80 range.

So you are saying that the cruising speed that I read to be the most efficient as said altitude (450kts) is a different value than the one I'm reading, right? As in ground speed vs air speed?

[Maki Nishikino]

Originally posted by WingedWolf9232:

Originally posted by Maki Nishikino:

Because what you're seeing on the airspeed indicator is indicated airspeed, this will be lower as you climb. You swap over to true airspeed / mach number. 1.32 mach is way too fast. I don't know the exact numbers but it should be in the .80 range.

So you are saying that the cruising speed that I read to be the most efficient as said altitude (450kts) is a different value than the one I'm reading, right? As in ground speed vs air speed?

From indicated yes.

https://en.wikipedia.org/wiki/True_airspeed

[Winged Wolf]

I see, thank you two :) you are the kind of people who make this a great community <3

[Maki Nishikino]

Glad to help! :D